The present invention is directed generally to molds for use in injection molding machines and to related apparatus used in conjunction with the molds to process articles produced in the molds. The invention pertains to the operation of elements for causing relative movement of some portions of the molds with respect to other portions, particularly in conjunction with the motion of the related molded article processing apparatus. The present invention is more particularly related to such apparatus for use in three portion molds consisting essentially of a mold cavity assembly, a mold core assembly and an intermediate assembly including space surface defining elements that cooperate with the mold core and cavity assemblies to define the space in which articles are molded of plastic, the apparatus regulating the movement of the space surface defining elements during movement of the intermediate assembly relative to the other portions of the mold and relative to the related molded article processing apparatus. The invention has particular utility in a molding operation in which the related molded article processing apparatus comprises a molded article receiver unit designed to enter into an interval or opening between the mold cavity assembly and the other mold assemblies subsequent to formation of the molded article. Of particular interest is the controlled positioning and/or timing of release of the molded article from the intermediate assembly into the molded article receiver unit.
Brun, Jr., et al., U.S. Pat. No. 5,531,588 discloses an adjustable cam track for a mold having a mold cavity assembly, a mold core assembly that is movable relative to the mold cavity assembly, and a stripper assembly movably interposed between the mold core and cavity assemblies. The stripper assembly has at least one pair of space defining surfaces that together with the mold cavity and core assemblies, defines at least one space for receiving plastic material injected therein to form at least one molded article. The mold core assembly and the stripper assembly can be moved away as a coupled pair from the mold cavity assembly to remove the at least one molded article from the mold cavity assembly. The mold core assembly and the stripper assembly are then separated to remove the at least one molded article from the mold core assembly. The adjustable cam track of Brun, Jr., et al., includes a guide fixed to the stripper assembly. A cam follower is coupled to the space defining surfaces of the stripper assembly platen and is engaged in the adjustable cam track so that movement of the cam follower causes movement of each pair of space defining surfaces relative to each other to release the molded article from the molding machine. The adjustable a cam track also includes a cam insert that is adjustably positionable with respect to the guide to adjust the point of release of the molded article. The cam insert includes a first toothed rack, and a second toothed rack removably fixed to the guide and engaging the first toothed rack to fix the position of the cam insert relative to the guide only at certain preselected locations.
The previously described adjustable cam track of Brun, Jr., et al., has been used in the manufacture of parisons for containers at rates that required special handling of the parisons upon their removal from the mold core assembly. This special handling was accomplished with a molded article receiver assembly that was movable into the interval between the mold cavity assembly and the mold core assembly when the mold was in an open position such as that disclosed in Delfer III, U.S. Pat. No. 4,721,452. Ideally, the position of the molded article receiver assembly was such that movement of the stripper assembly relative to the mold core assembly inserted the parisons into the molded article receiver assembly. This was followed immediately by the release of the parisons by the pair of space defining surfaces, which only occurred when the parisons were properly located in the molded article receiver assembly. However, as a practical matter, even slight misalignment between the mold core assembly and the molded article receiver assembly caused one or more of the parisons to be significantly damaged as they were inserted into the molded article receiver assembly. Furthermore, since release of the parisons was related only to the relative position of the stripper assembly relative to the mold core assembly, is was also necessary to accurately position the molded article receiver assembly and coordinate the timing of such positioning so that as little damage as possible occurred. While substantial efforts were focused on insuring the proper alignment between the mold core assembly and the molded article receiver assembly during the movement of the stripper assembly, this did not always accomplish the desired end.
In co-pending U.S. application Ser. No. 09/726,743, filed Nov. 30, 2000 and assigned to the same assignee, an adjustable cam track is disclosed that includes a guide coupled to a mold core assembly, the guide defining a first portion of the adjustable cam track. A cam follower is engaged in the cam track and is coupled to the space defining surfaces carried by the stripper assembly for causing relative movement of each pair of space defining surfaces as the stripper assembly moves relative to the mold core assembly. The cam follower is engaged in the first portion of the cam track when the mold portions are in the closed position. The first portion of the cam track also includes a ramp to an intermediate portion defining the prerelease position of each pair of space defining surfaces so that the molded article is loosely retained by the space defining surfaces. This loose retention accommodates for any small amount of misalignment between the molded article receiver assembly during the transfer of the molded articles from the stripper assembly to the molded article receiver assembly. The adjustable cam track of the co-pending application also includes a cam insert defining a second portion of the adjustable cam track. The path defined by the cam insert is generally a matter of choice of design except that it defines the point of release of the molded article from the space defining surfaces. The cam insert is adjustably positionable with respect to the guide to adjust the point of release with respect to the ramp defining the onset of prerelease, thereby permitting the adaptation of the cam track to molded articles of a variety of sizes. However this adjustment of position of the cam insert is one made to generally coordinate the position of the release, but is not responsive to the timing of the achievement of the specified position by the molded article receiver apparatus.
It is therefore desirable that each pair of space defining surfaces of the stripper assembly be allowed to separate slightly, but not entirely, from the molded articles so that the molded articles are only loosely retained in a prerelease position. This prerelease position allows some play in the position of the molded articles relative to the stripper assembly thus permitting some variation in position of the molded article receiver assembly at the time of introduction of the molded articles. Due to the variation in length of the molded articles, it is also desirable to modify or adjust the position of product release from the stripper assembly in relation to the position of onset of the prerelease position. It is also desirable for the product release from the stripper assembly to occur in response to an indication of the attainment of a specified position by the molded article receiver assembly.
Accordingly, an article molding assembly of the present invention includes a mold and a release mechanism for releasing molded articles from the mold. The mold includes a first mold portion, a second mold portion that is movable with respect to the first mold portion, and a third mold portion. The third mold portion is movably interposed between the first and second portions and has at least one pair of space defining surfaces which, together with the first and second mold portions, defines in a closed position at least one space for receiving plastic material injected therein to form one or more molded articles. The second and the third mold portions are movable away from the first mold portion to permit removal of the molded articles from the first mold portion. The second mold portion is also movable away from the third mold portion to remove the molded articles from the second mold portion. The release mechanism operates to release the molded articles from the third mold portion. In an embodiment of particular interest, the first mold portion is a mold cavity plate including a plurality of cavities and the second mold portion is a mold core plate supporting a like plurality of cores adapted to inserted into the cavities when the mold is in a closed position. The third mold portion is a stripper plate that supports a like plurality of sets of engaging elements such as thread splits. The thread splits or other similar elements function, in conjunction with the core and cavity portions of the mold, to define the spaces into which plastic can be injected to form the articles having a desired configuration. The release mechanism acts to release the molded articles from the thread splits or similar article engaging elements, generally into a cooling mechanism that will complete the cooling cycle needed for the formation of the molded articles, thereby shortening the residence time of the molded articles in the mold subsequent to injection.
The release mechanism of the present invention includes a guide coupled to the second mold portion. The guide controls the relative position of the sets of space defining surfaces that, together with a first and second mold portions, define in the closed position the space for receiving injected plastic material to form the molded articles. The guide generally includes a first portion having a closed end and including a pair of inner sides confronting each other to define a cam track. The inner sides in the first portion are spaced sufficiently from each other to accommodate a cam follower that is closely received between the inner sides when the mold portions are in the closed position. The first portion can also include a ramp leading to an intermediate portion. The intermediate portion functions to define a pre-release position for the pairs of space defining surfaces so that the molded articles are loosely retained by the space defining surfaces. In a preferred embodiment, one of the inner sides in the intermediate portion is inclined away from the other inner side thus expanding the space that can be occupied by the cam follower toward a second portion. The second portion includes an open end so that the cam follower can move outside the space between the inner sides of the cam track. Further, the inclined away inner surface is adapted to contact the cam follower as the third mold portion moves from the full release position toward the second mold portion. The cam follower then travels along the inclined away inner surface to return the space defining surfaces to a closed position.
As has already been indicated, a cam follower that is coupled to the sets of space defining surfaces of the third mold portion is engaged in the cam track when the second and third mold portions are within a pre-selected distance of each other. The cam follower interacts with the inner surfaces of the cam track to cause relative movement of the sets of space defining surfaces. The cam follower is generally closely engaged in the first portion of the cam track when the mold portions are in the closed position. The cam follower can be less closely engaged in the intermediate portion defining the pre-release position of the sets of space defining surfaces. The cam follower can be completely outside the cam track defined by the confronting inner surfaces at the point of full release of the molded articles.
The release is achieved by a power operator, such as a fluid operated cylinder, solenoid, or other similar device carried by the third mold portion and coupled to the space defining surfaces. The power operator is responsive to a signal to move the sets of space defining surfaces from the pre-release position to a full release position. In the preferred embodiment the signal is supplied by a molded article receiver in sufficiently close proximity to the third mold portion that the molded articles are transferred from the third mold portion to the molded article receiver at such time as the articles are released by the sets of space defining surfaces.
In a particularly desirable embodiment, the molded article receiver includes at least one corresponding receiver tube alignable with each set of space defining surfaces for receiving the molded article, and at least one sensor for detecting any deposition of a molded articles into a receiver tube, the sensor being coupled to a signal source for sending said signal to said power operator. In this embodiment the receiver tube can include an open forward end configured to receive a molded article and a closed rearward end having a surface contact element movably situated with respect to the forward end and configured to conform to a portion of the surface of the molded article. A vacuum duct couples to the closed rearward end of the receiver tube to a source of vacuum for assisting in the retention of a molded article within the receiver tube. An air cylinder is coupled to the surface contact element, and a pressure duct couples each air cylinder to a source of air pressure for controlling the position of the surface contact element with respect to the forward end of the receiver tube.
In the usual operation of an injection molding machine, molded articles are formed in a mold having a first mold portion, a second mold portion movable with respect to the first mold portion. In molding machines of particular interest to the present invention, a third mold portion is movably interposed between the first and second portions that has at least one pair of space defining surfaces for each space defined between the first and second mold portions for receiving plastic material to form molded articles. The second and the third mold portions generally are movable relative to the first mold portion to permit removal of the molded articles from the first mold portion. The second mold portion is movable relative to the third mold portion to permit removal of the molded articles from the second mold portion. When the second and third mold portions have moved as a unit sufficient distance to remove the molded articles from contact with the first mold portion and provide a gap between the first and second mold portions, a molded article receiver moves into proximity with the third mold portion. The present invention is directed toward removing the molded articles from the third mold portion and introducing the molded articles into the receiver for further treatment, generally cooling, without damaging the newly molded articles.
The release of the molded articles from the third mold portion into the molded article receiver is accomplished by providing a guide coupled to the second mold portion that forms a cam track. A cam follower is coupled to the pairs of space defining surfaces of the third mold portion, the cam follower engaging the cam track at least when the second and third mold portions are in a closed position as well as when second and third mold portions are within a pre-selected distance of each other. While the cam track and follower are engaged, the cam follower interacts with the cam track to cause relative movement of each pair of space defining surfaces. As the third mold moves toward the molded article receiver, the cam follower moves to a portion of the cam track including a ramp defining a pre-release position of each pair of space defining surfaces mounted to the third mold portion so that the molded articles are loosely retained by the space defining surfaces. In this loosely retained position, the articles can be inserted into appropriate receivers, such a receiving tubes, despite some amount of misalignment between the receivers and the molded articles. This has the advantage of reducing the amount of damage suffered by the newly molded articles and prevents any machine lock-up due to minor misalignment between the molded article receiver and the articles being held by the third portion of the mold. Additional insertion of the molded article into the molded article receiver is achieved by movement of the third mold portion even further away from the second mold portion, to a point where the cam is no longer captured in the cam track and no longer controls the position of the pairs of space defining surfaces.
Once the molded articles are at least partially received in the receiver elements or tubes of the molded article receiver through movement of the third mold portion away from the second mold portion, a signal is provided to a power operator carried by the third mold portion and coupled to the space defining surfaces. The signal causes the power operator to move each pair of space defining surfaces from the pre-release position toward a full release position for releasing the molded articles from the third mold portion into the molded article receiver. The signal can be provided by a proximity detector situated on the third mold portion that senses, for example, the position of the third mold portion in relation to either the second mold portion or preferably the molded article receiver. A signal can also be provided by a sensor situated on the molded article receiver that senses, for example, the position of the third mold portion or preferably any deposit of molded articles into a receiver tube of the molded article receiver. In any case, the sensor is generally coupled to a signal generator capable of sending a signal to the power operator situated on the third mold portion. Desirably, the signal causing the power operator to move the space defining surfaces on the third mold portion is generated before the molded articles are fully deposited into the receiver elements or tube of the molded article receiver. This has the advantage of preventing damage to the portion of the molded article being held by the space defining surfaces that might occur if completed positioning is required prior to release due to xe2x80x9cbottoming outxe2x80x9d of the molded article within the article receiver element or tube.
Further avoidance of damage caused by xe2x80x9cbottoming outxe2x80x9d can be achieved by providing within each receiver tube an open forward end configured to receive a molded article and a closed rearward end including a surface contact element movably situated with respect to the forward end. The surface contact element is configured to conform to a portion of the surface of the molded article, and to be easily moved away from the forward end by contact with a molded article as it is deposited within the tube. To assist in this rearward movement, the closed rearward end of the receiver tube is coupled to a source of vacuum. There is also an air cylinder coupled to the movable surface contact element, the air cylinder being provided with sufficient air pressure to bias the surface contact element toward the open forward end of the receiver tube. The vacuum coupled to the closed rearward end of the receiver tube is generally insufficient to overcome the bias provided to the surface contact element by the air pressure within the air cylinder when no molded article is present within the receiver tube. However, when a molded article is located within the receiver tube, the vacuum becomes enhanced and assists in locating a molded article within the receiver tube in contact with the surface contact element. This vacuum action had the advantage of centering the molded article within the receiving tube so that the spacing of the cooling tubes now controls the spacing of the molded articles, even though the article spacing may have varied from that dimension due to the loose holding arrangement between the molded articles and the pairs of space defining surfaces prior to insertion of the molded articles into the receiving tubes.
In a particularly desirable embodiment, the signal, which causes operation of the power operator on the third mold portion releasing the molded articles from the space defining surfaces, is provided said signal from the molded article receiver to said power operator to cause movement of each pair of space defining surfaces from the pre-release position to a full release position only after the molded article is in contact with the surface contact element. This ensures that the molded articles are suitably positioned to allow the vacuum to overcome the bias provided by the air pressure within the air cylinders so that the surface contact element and molded article are displaced toward the receiver tube closed end thus uncoupling the molded article from the third mold portion, usually causing a displacement of the molded article away from the plane generally defined by the third mold portion. The release of the molded articles from the space defining surfaces under operation of the vacuum is sufficiently gentle that the surfaces of the molded articles held by the space defining surfaces are not damaged during the release process.
After the molded articles are safely situated in the molded article receiver, the molded article receiver is withdrawn from the gap between the first and second mold portions. After a suitable lapse of time and after the molded article receiver is moved to a suitable location, the air cylinder is provided with sufficient air pressure to displace the surface contact element toward the open end with sufficient speed to eject the molded article from the receiver tube for further processing. Generally, subsequent to the release of the molded articles from the pairs of space defining surfaces, and at the same time that the molded article receiver is removed from the gap between the first and second mold portions, the third mold portion is moved back toward the second mold portion so that the cam follower re-enters the cam track. The cam track is provided with an inclined surface adapted to contact the cam follower as the third mold portion moves from the full release position toward the second mold portion. This contact between the cam follower and inclined surface of the cam track returns the space defining surfaces to a closed position. This operation has the advantage of ensuring the repeatability of the positioning of the space defining surfaces without requiring very highly calibrated power operators coupling the space defining surfaces to the third mold portion.
Other features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the illustrated preferred embodiment shown in the accompanying figures showing the best mode of the present invention as understood by the inventors.